1. Field of the Invention
This invention relates to an automatically operated speed-changing apparatus (transmission) of an automobile and an industrial vehicle. In particular, it relates to the automatically operated speed-changing apparatus in which an operating mechanism to change a gear speed changing mechanism for speed-changing is automatically operated by a hydraulically or electrically operated actuator, and a controlling method therefor.
2. Related Art
In a transmission of an automobile, there is an automatically operated transmission in which a speed-changing operation for changing combination of gears of a gear train is automatically carried out by an actuator of a hydraulic type or an electrical type, based on a driver's manual handling.
FIG. 4 shows one example of such automatically operated transmission which is comprised of a gear speed-changing mechanism 2, an operating mechanism for setting a predetermined speed-changing ratio by changing combination of meshing gears i.e. transmitting condition of the gear speed-changing mechanism 2, actuators 4 and 5 for hydraulically or electrically driving the operating mechanism 3, and a controlling means 6 for controlling the actuators 4 and 5, all of which are disposed in a speed-changing case 1. The controlling means 6 controls the actuators 4 and 5 based on a signal generated by handling of a manually operated shift member 7 such as a switch or lever. The controlling means 6 is constructed by a hydraulically controlled device when the actuators 4 and 5 are of hydraulically-operated type, while it is constructed by a ECU (Electrically Controlled Unit) when the actuators 4 and 5 are electrical motors.
The automatically operated transmission shown in FIG. 4 is for a manually operated transmission (manual transmission), so the gear speed-changing mechanism 2 is comprised of constantly meshed type gear train mounted on an input shaft, a counter shaft and an output shaft (driven shaft), and transmitting condition or combination of the gears thereof is changed by the operating mechanism 3 to set (shift) a predetermined speed-changing ratio.
The operating mechanism 3 is comprised of a synchromesh mechanism in which a relative braking is generated by a coned friction surface thereof, and a shift fork engaged with a sleeve of the synchromesh mechanism. The synchromesh mechanism is, as shown in FIG. 5, provided with the sleeve 8 which has inner peripheral splines 8a meshing with outer peripheral splines of a clutch hub (not shown), a synchronizer ring 9 of cone-shape and is pushed in an axial direction of X by the sleeve 8, and a key 10 fitted on an inner peripheral surface of the sleeve 8 centrifugally and pushes an end surface of the synchronizer ring 9 in the axial direction X in an initial period (this is called as "shift put-in area") of the shifting operation of the sleeve 8. The key 10 is positioned on the inner peripheral surface of the sleeve 8 to be rotated at a position offset toward one side of a groove of an outer peripheral tooth 9b of the synchronizer ring 9. Therefore, when the sleeve 8 is shifted in the axial direction x by the shift fork 12, as shown in FIG. 6, the sleeve 8 and the synchronizer ring 9 are opposed in a phase where a chamfered surface 8b of the inner peripheral splines 8 a and a chamfered surface 9a of the outer peripheral teeth 9b are offset in a circumferential direction.
That is, in the synchromesh mechanism, when the sleeve 8 positioned at the neutral position is shifted by the shift fork 12 in the axial direction X so that the key 10 presses the end surface of the synchronizer ring 9 in the axial direction X (shift push-in area), as shown in FIG. 6, the chamfered surface 8b of the sleeve 8 and the chamfered surface 9a of the synchronizer ring 9 regulate the inner peripheral splines 8a of the sleeve 8 and the outer peripheral gears 9b of the synchronizer ring 9 in a state where they are offset with each other by width of the key 10 (synchronize area). Thus, the sleeve 8 further shifts in the axial direction X to press the chamfered surface 9a of the synchronizer ring 9 by the chamfered surface 8b thereof, so that the inner peripheral splines 8a of the sleeve 8 put into the adjacent grooves of the outer peripheral teeth 9b of the synchronizer ring 9. This period is called as "push-apart area", and the push-apart completes when the number of rotations of a gear 11 coincides with that of the synchronizer ring 9 due to direct pushing by the sleeve 8 to the synchronizer ring 9. In state where the push-apart is completed, since the synchronizer ring 9 can be freely rotated, the sleeve 8 is shifted in the axial direction x by the shift fork 12 driven by the actuators 4 and 5, so that the inner peripheral splines 8a of the sleeve 8 put into the adjacent grooves of outer teeth lla of the gear 11 (this period is called as "piece mesh area"), to complete the speed-changing.
The actuators 4 and 5 apply an axial load to a shift fork 12 of the operating mechanism 3, and a hydraulic cylinder or hydraulic motor is used as the hydraulic type actuator, while an electric motor is used as the electric type actuator. When the gear speed changing mechanism 2 is operated via the operating mechanism 3 by the actuators 4 and 5 of the hydraulic or electric type, the actuators 4 and 5 should assume position to press the sleeve 8 for maintaining the gear speed-changing mechanism 2 in a state where a predetermined speed-changing ratio is set. However, the axial load applied to the actuators 4 and 5 to press the sleeve 8 axially is relieved at the time when the shifting operation of the operating mechanism 3 including the sleeve 8 is completed, and the sleeve 8 is then retained at the present position by a ball-lock mechanism in the transmission.
However, if shock is applied to the vehicle due to sudden acceleration or deceleration of running speed, running on a rough (convex/concave) surface, or running over a step, load in a reverse direction to the force applied by the ball locking mechanism is applied to the sleeve 8 of the operating mechanism 3 which has reached to the shift completing position to retract the sleeve 8 to the piece-mesh area, the push-apart area or the synchronizing area to thereby cause "a shift-fall". In the shift fallen state, the gear speed-changing mechanism 2 becomes a neutral state where a gear rotating together with the output shaft freely rotates relative to the output shaft, so that the driver feels uneasiness due to unintentional running of the vehicle.
For restoring or returning the neutral state of the gear speed-changing mechanism 2 to the original shifted state automatically, the shift-fall of the synchromesh mechanism may possibly be detected by a stroke sensor disposed in the actuators 4 and 5 corresponding to the shift push-in area of the synchromesh mechanism, and the actuators 4 and 5 are operated again, based on the output of the actuators 4 and 5 for driving the operating mechanism 3. However, if the synchromesh mechanism is always driven again to the shift completing position based on detection of the synchromesh mechanism at the shift push-in area via the synchronizing area, the push-apart area and piece-mesh area, the driver is left in the unintentional running state for a long time.